(E) Important Quotation: "the risk of tipping cascades [to destabilizing feedbacks] could be significant at a 2°C temperature rise and could increase sharply beyond that point. We argue that a planetary threshold in the Earth System could exist at a temperature rise as low as 2°C above preindustrial," from
Will Steffen, Johan Rockström, Katherine Richardson, et al. (2018) 'Trajectories of the Earth System in the Anthropocene.' Proceedings of the National Academy of Sciences (USA) 115 (33): 8252-8259.